Car Stereos: Engine noise and whine thru speakers, gauge wires, scion xb

Question
This topic has been run in the ground and I am failing to find any new answers to solve my problem.  Hoping you can help.  I just installed a new head unit (Pioneer) in a 2006 Scion xB. The rear channel from the HU runs the rear spkrs directly.  RCA outs go to a nice JBL amp located under the passenger seat. I ran the 8 guage power cable directly to the battery along the driver's door sill.  I ran a short ground jumper (8 guage) from the amp to the seat mounting bolt (sanded to shiny metal).  RCA, remote turn on, and speaker wires were run along the passenger door sill.  The noise is intolerable. I have done trouble shooting as follows:
-Ran different RCAs separately from the HU to the amp without ANY contact with other wires-no help.
-Ran a different gound attaching it to a factory ground.  Also tried running a ground straight to the neg post-no help.
-Installed filter infront of RCAs-helped, but not sufficiently.
-Ran amp ground directly to factory stero ground-no help.
-Ran power cable off of distribution block rather than positive post-no help.

I have changed amps, changed speakers, changed wiring...nothing helps.  This has to be a Scion xB quirk.  There is no noise coming from my rear speakers which go directly to the head unit.  Only the amp signal is tainted.

Jason


Answer
Hi Jason,

Some vehicles are worse than others for ground looping.  Look around online for 'ground kits'.  Some companies sell them for specific models of vehicles.  They're basically precut heavy gauge wires that you install in various areas to make the factory system have less EMI.

Make sure your ground wire from the amp to the chassis is as short as possible, and don't connect it to somewhere other parts are connected.  Give it its own hole, and make sure it goes through a non-welded, sanded clean part of the body with a washer and gets bolted tightly.  If you have heated seats, you might want to move the amp somewhere else in the vehicle, as any electronics that are responsible for generating heat will also give off retarded amounts of EMI.

Good luck,
Justin